rivers and streams final exam Flashcards
What is the hydrologic cycle?
It is how the water on earth rotates among different processes from the sea to the atmosphere to the land.
What is a permanent stream?
A permanent stream is one that lies below the table water line.
What is an ephemeral stream?
An ephemeral stream is one that lies above the table water line
What is a braided stream?
A stream that has inter-fingering branch streams crisscrossing
What is a meandering stream?
A snake like stream that has kinks and loops
What is a point bar and cut bank and how do they form?
A point bar - area of deposition, corner of a meander, forms due to high velocity engaging a corner
a cut bank - area of erosion, forms due to the stream hitting the edge of the land causing a meander neck, which eventually erode due to constant erosion
Where does erosion and deposition occur along a meandering stream?
A point bar creates deposition while a cut bank creates erosion
How does a floodplain form?
Flood plains form when rivers erode their own banks and redeposit the eroded material downstream. They form due to the action of the river until it becomes a flat floodplain as a result of over bank deposition.
How do deltas form?
Deltas form in result of the low course of the river slowing down and the stream entering standing waters. The stream will then divide into multiple tributaries that go into the ultimate base level
What is a drainage basin?
One river acting as a father river of other branching streams that flow into it, not like a braided stream
How is sediment transported in rivers?
The river can carry specific types of loads depending on its velocity, competence, and capacity.
What is discharge?
Discharge is the amount of water a given stream can hold
what is a hydrograph?
a graph that tracks the rainfall/discharge from floods over time
How is discharge related to stream size?
The two are related because certain streams can only hold how much the can fit. So for example, one stream may have a larger discharge than a smaller stream based on SIZE
How does discharge effect flood events?
Discharge affects flood events overflowing the given amount a river can actually hold
Difference between competence and capacity?
Competence is the size of particle a river can move. Capacity is the amount of those particles.
How is the energy of the stream related to the size of particles it can carry and deposit?
A stream’s velocity and size can affect the type of load it can move throughout. If the energy is low, then it may not be able to move large boulders and pebbles but can move silt and clay (vice versa)
Why are large boulders the size of houses able to be moved during a flood?
Boulders can be moved during a flood because the water amount has increased and when there is more water on a given gradient, the energy level can be increased due to the velocity increasing. In result, the capacity and competence increased
What is the difference between an alluvial fan and a delta?
delta’s form at the lower course of a stream and break of into an ocean (or base level). An alluvial fan forms on dry land while deltas form when entering water
What is an alluvial fan?
a triangle shape/cone shaped deposit in result from stream deposits usually on dry land
What triggers flooding?
Heavy rainfall, snow melting off, or failure of a dam or levee
Costliest and most common natural hazard, more water coming down a channel than it can actually hold
flood
smaller and short lived floods; intense rain event in smaller area, flood occurs after rain event; doesn’t affect areas down stream
upstream floods
Long lived flood; huge amount of water; large river systems involved; adds up flooding in tributaries; more devastating damage
downstream floods
flood where water rises rapidly with little warning; the ground in impermeable that it collects water easily
flash flood
what causes flash floods
intense rainfall or dam failures - can be destructive
barrier that restricts the movement of rivers and narrows the channels; increases depth in channel
Levees
How do urban areas deal with flooding?
Since there is no groundwater to soak up the water, it drains off and are very short lived floods (upstream)
How do we control floods
Create levees, put most important buildings away from flood plain, stop developing in floodplain, urbanization
Some ways for flood hazard mitigation?
Restore the channel; determine where water will be different
